How is it possible to record optically encoded information for distances smaller than the wavelength of light?

Researchers at the University of Illinois at Urbana-Champaign have demonstrated that an array of novel gold, pillar-bowtie nanoantennas (pBNAs) can be used like traditional photographic film to record light for distances that are much smaller than the wavelength of light (for example, distances less than ~600 nm for red light). A standard optical microscope acts as a “nanocamera” whereas the pBNAs are the analogous film.

Here’s an image the researchers have provided to illustrate their work,

We demonstrate the plasmonic equivalent of photographic film for recording optical intensity in the near field. The plasmonic structure is based on gold bowtie nanoantenna arrays fabricated on SiO2 pillars. We show that it can be employed for direct laser writing of image data or recording the polarization structure of optical vector beams.[downloaded from http://pubs.acs.org/doi/abs/10.1021/nl501788a]

The news release describes the technique,

“Unlike conventional photographic film, the effect (writing and curing) is seen in real time,” explained Kimani Toussaint, an associate professor of mechanical science and engineering, who led the research. “We have demonstrated that this multifunctional plasmonic film can be used to create optofluidic channels without walls. Because simple diode lasers and low-input power densities are sufficient to record near-field optical information in the pBNAs, this increases the potential for optical data storage applications using off-the-shelf, low-cost, read-write laser systems.”

“Particle manipulation is the proof-of-principle application,” stated Brian Roxworthy, first author of the group’s paper, “Multifunctional Plasmonic Film for Recording Near-Field Optical Intensity,” published in the journal, Nano Letters. “Specifically, the trajectory of trapped particles in solution is controlled by the pattern written into the pBNAs. This is equivalent to creating channels on the surface for particle guiding except that these channels do not have physical walls (in contrast to those optofluidics systems where physical channels are fabricated in materials such as PDMS).”

To prove their findings, the team demonstrated various written patterns—including the University’s “Block I” logo and brief animation of a stick figure walking—that were either holographically transferred to the pBNAs or laser-written using steering mirrors (see video).

The news release concludes with,

“We wanted to show the analogy between what we have made and traditional photographic film,” Toussaint added. “There’s a certain cool factor with this. However, we know that we’re just scratching the surface since the use of plasmonic film for data storage at very small scales is just one application. Our pBNAs allow us to do so much more, which we’re currently exploring.”

The researchers noted that the fundamental bit size is currently set by the spacing of the antennas at 425-nm. However, the pixel density of the film can be straightforwardly reduced by fabricating smaller array spacing and a smaller antenna size, as well as using a more tightly focusing lens for recording.

“For a standard Blu-ray/DVD disc size, that amounts to a total of 28.6 gigabites per disk,” Roxworthy added. “With modifications to array spacing and antenna features, it’s feasible that this value can be scaled to greater than 75 gigabites per disk. Not to mention, it can be used for other exciting photonic applications, such as lab-on-chip nanotweezers or sensing.”

“In our new technique, we use controlled heating via laser illumination of the nanoantennas to change the plasmonic response instantaneously, which shows an innovative but easy way to fabricate spatially changing plasmonic structures and thus opens a new avenue in the field of nanotech-based biomedical technologies and nano optics,” said Abdul Bhuiya, a co-author and member of the research team.

Researchers, Ingrid Bergin in the Unit for Laboratory Animal Medicine, at the University of Michigan in Ann Arbor and Frank Witzmann in the Department of Cellular and Integrative Physiology, at Indiana University School of Medicine, in Indianapolis, have stated that ingesting food and beverage (translated by me from the more scientific description) with nanoparticles (at today’s current levels) is unlikely to prove toxic. A June 26, 2013 Inderscience news release on EurekAlert describes the researchers’ research and their conclusions,

Writing in a forthcoming issue of the International Journal of Biomedical Nanoscience and Nanotechnology, researchers have compared existing laboratory and experimental animal studies pertaining to the toxicity of nanoparticles most likely to be intentionally or accidentally ingested. Based on their review, the researchers determined ingestion of nanoparticles at likely exposure levels is unlikely to cause health problems, at least with respect to acute toxicity. Furthermore, in vitro laboratory testing, which often shows toxicity at a cellular level, does not correspond well with in vivo testing, which tends to show less adverse effects.

Ingrid Bergin in the Unit for Laboratory Animal Medicine, at the University of Michigan in Ann Arbor and Frank Witzmann in the Department of Cellular and Integrative Physiology, at Indiana University School of Medicine, in Indianapolis, explain that the use of particles that are in the nano size range (from 1 billionth to 100 billionths of a meter in diameter, 1-100 nm, other thereabouts) are finding applications in consumer products and medicine. These include particles such as nano-silver, which is increasingly used in consumer products and dietary supplements for its purported antimicrobial properties. Nanoparticles can have some intriguing and useful properties because they do not necessarily behave in the same chemical and physical ways as non-nanoparticle versions of the same material.

Nanoparticles are now used as natural flavor enhancers in the form of liposomes and related materials, food pigments and in some so-called “health supplements”. They are also used in antibacterial toothbrushes coated with silver nanoparticles, for instance in food and drink containers and in hygienic infant feeding equipment. They are also used to carry pharmaceuticals to specific disease sites in the body to reduce side effects. Nanoparticles actually encompass a very wide range of materials from pure metals and alloys, to metal oxide nanoparticles, and carbon-based and plastic nanoparticles. Because of their increasing utilization in consumer products, there has been concern over whether these small scale materials could have unique toxicity effects when compared to more traditional versions of the same materials.

Difficulties in assessing the health risks of nanoparticles include the fact that particles of differing materials and shapes can have different properties. Furthermore, the route of exposure (e.g. ingestion vs. inhalation) affects the likelihood of toxicity. The U.S. researchers evaluated the current literature specifically with respect to toxicity of ingested nanoparticles. They point out that, in addition to intentional ingestion as with dietary supplements, unintentional ingestion can occur due to nanoparticle presence in water or as a breakdown product from coated consumer goods. Inhaled nanoparticles also represent an ingestion hazard since they are coughed up, swallowed, and eliminated through the intestinal tract.

Based on their review, the team concludes that, “Ingested nanoparticles appear unlikely to have acute or severe toxic effects at typical levels of exposure.” Nevertheless, they add that the current literature is inadequate to assess whether nanoparticles can accumulate in tissues and have long-term effects or whether they might cause subtle alterations in gut microbial populations. The researchers stress that better methods are needed for correlating particle concentrations used for cell-based assessment of toxicity with the actual likely exposure levels to body cells. Such methods may lead to better predictive value for laboratory in vitro testing, which currently over-predicts toxicity of ingested nanoparticles as compared to in vivo testing.

The researchers focused specifically on ingestion via the gastrointestinal tract which I take to mean that they focused largely on nanoparticles in food (eaten) and liquid (swallowed).

The increasing interest in nanoparticles for advanced technologies, consumer products, and biomedical applications has led to great excitement about potential benefits but also concern over the potential for adverse human health effects. The gastrointestinal tract represents a likely route of entry for many nanomaterials, both directly through intentional ingestion or indirectly via nanoparticle dissolution from food containers or by secondary ingestion of inhaled particles. Additionally, increased utilisation of nanoparticles may lead to increased environmental contamination and unintentional ingestion via water, food animals, or fish. The gastrointestinal tract is a site of complex, symbiotic interactions between host cells and the resident microbiome. Accordingly, evaluation of nanoparticles must take into consideration not only absorption and extraintestinal organ accumulation but also the potential for altered gut microbes and the effects of this perturbation on the host. The existing literature was evaluated for evidence of toxicity based on these considerations. Focus was placed on three categories of nanomaterials: nanometals and metal oxides, carbon-based nanoparticles, and polymer/dendrimers with emphasis on those particles of greatest relevance to gastrointestinal exposures.

In spring 2012, there was a fluttering in the blogosphere about tooth tattoos with the potential for monitoring dental health. As sometimes happens, I put off posting about the work until it seemed everyone else had written about it (e.g. Mar. 30, 2012 posting by Dexter Johnson for his Nanoclast blog on the IEEE website) and there was nothing left for me to say. Happily, the researchers at Tufts University (where part of this research [Princeton University is also involved] is being pursued) have released more information in a Nov. 1, 2012 news article by David Levin,

The sensor, dubbed a “tooth tattoo,” was developed by the Princeton nanoscientist Michael McAlpine and Tufts bioengineers Fiorenzo Omenetto, David Kaplan and Hu Tao. The team first published their research last spring in the journal Nature Communications.

The sensor is relatively simple in its construction, says McAlpine. It’s made up of just three layers: a sheet of thin gold foil electrodes, an atom-thick layer of graphite known as graphene and a layer of specially engineered peptides, chemical structures that “sense” bacteria by binding to parts of their cell membranes.

“We created a new type of peptide that can serve as an intermediary between bacteria and the sensor,” says McAlpine. “At one end is a molecule that can bond with the graphene, and at the other is a molecule that bonds with bacteria,” allowing the sensor to register the presence of bacteria, he says.

Because the layers of the device are so thin and fragile, they need to be mounted atop a tough but flexible backing in order to transfer them to a tooth. The ideal foundation, McAlpine says, turns out to be silk—a substance with which Kaplan and Omenetto have been working for years.

By manipulating the proteins that make up a single strand of silk, it’s possible to create silk structures in just about any shape, says Omenetto, a professor of biomedical engineering at Tufts. Since 2005, he’s created dozens of different structures out of silk, from optical lenses to orthopedic implants. Silk is “kind of like plastic, in that we can make [it] do almost anything,” he says. “We have a lot of control over the material. It can be rigid. It can be flexible. We can make it dissolve in water, stay solid, become a gel—whatever we need.”

Omenetto, Kaplan and Tao created a thin, water-soluble silk backing for McAlpine’s bacterial sensor—a film that’s strong enough to hold the sensor components in place, but soft and pliable enough to wrap easily around the irregular contours of a tooth.

To apply the sensor, McAlpine says, you need only to wet the surface of the entire assembly—silk, sensor and all—and then press it onto the tooth. Once there, the silk backing will dissolve within 15 or 20 minutes, leaving behind the sensor, a rectangle of interwoven gold and black electrodes about half the size of a postage stamp and about as thick as a sheet of paper. The advantage of being attached directly to a tooth means that the sensor is in direct contact with bacteria in the mouth—an ideal way to monitor oral health.

Because the sensor doesn’t carry any onboard batteries, it must be both read and powered simultaneously through a built-in antenna. Using a custom-made handheld device about the size of a TV remote, McAlpine’s team can “ping” that antenna with radio waves, causing it to resonate electronically and send back information that the device then uses to determine if bacteria are present.

The sensor (A), attached to a tooth (B) and activated by radio signals (C), binds with certain bacteria (D). Illustration: Manu Mannoor/Nature Communications (downloaded from http://now.tufts.edu/articles/tooth-tattoo)

In addition to its potential for monitoring dental health, the tooth tattoo could replace some of the more invasive health monitoring techniques (e.g., drawing blood), from the Tufts University article,

In addition to monitoring oral health, Kugel [Gerard Kugel, Tufts professor of prosthodontics and operative dentistry and associate dean for research at Tufts School of Dental Medicine] believes the tooth tattoo might be useful for monitoring a patient’s overall health. Biological markers for many diseases—from stomach ulcers to AIDS—appear in human saliva, he says. So if a sensor could be modified to react to those markers, it potentially could help dentists identify problems early on and refer patients to a physician before a condition becomes serious.

“The mouth is a window to the rest of the body,” Kugel says. “You can spot a lot of potential health problems through saliva, and it’s a much less invasive way to do diagnostic tests than drawing blood.”

Before monitoring of any type can take place, there is at least one major hurdle still be overcome. Humans are quite sensitive to objects being placed in their mouths. According to one of the researchers, we can sense objects that are 50 to 60 microns wide, about the thickness piece of paper, and that may be too uncomfortable to bear.

I don’t hear much about New Zealand usually but two items popped up on the radar yesterday. There’s a nano art exhibit opening on Aug. 11, 2010 in Christchurch at Our City O-Tautahi, corner of Worcester Boulevard and Oxford Terrace. Admission is free. More from the news item on Voxy,

A new exhibition at Our City O-Tautahi merges art with the atom in an effort to explain nanotechnology.

Nanotechnology, one of the key technologies of the 21st Century, is probably the least understood despite being well on its way to becoming an integral part of our everyday lives.

Now the University of Canterbury and the MacDiarmid Institute for Advanced Material and Nanotechnology, in collaboration with artists and scientists, is offering a better understanding of nanotechnology through art.

Their exhibition: The Art of Nanotechnology at Our City O-Tautahi from Wednesday 11 August through to Friday 10 September presents intriguing nanotechnology images and art inspired by nanotechnology.

Researchers from around New Zealand were asked to enter the most interesting images from their work in a competition, and the best images are displayed in the exhibition. The MacDiarmid Institute for Advanced Materials and Nanotechnology, which is a government-funded Centre of Research Excellence, kindly donated $2000 in prizes.

Alongside these images are works from artists Claire Beynon (in a collaboration with biologist Sam Bowser), Nicola Gibbons, Sue Novell and Robyn Webster. These artists attempt to shed light on the incredible and tiny new worlds of nanotechnology. Each have selected one little corner of a vast subject, and examined it up close, just as a scientist uses a microscope.

This is one of a series of events being put on by the University of Canterbury this August. You can read more here.

Space junk

As for the space junk item, that comes from an article by Kit Eaton in Fast Company. 1992 was the first I heard that outer space was in fact a floating junk yard. For example, when satellites and other space equipment stop functioning, it’s easier to send a new model up then try and repair them. I imagine that in the 18 years since the situation has gotten worse. Amongst other ideas on how to clean things up, there’s this one (from the Fast Company article, The Most Beautiful Way to Clean Up Space Junk: A Giant GOLD Balloon),

Dr. Kristen Gates has one idea, and it’s beautiful and simple. It’s dubbed GOLD–the Gossamer Orbit Lowering Device–and it’s just been revealed at the “Artificial and Natural Space Debris” session of the AIAA Astrodynamics Specialists Conference.

GOLD is not much more than a football-field sized balloon (made of gossamer-thin but super-tough material, a little like solar sails) that is flown into orbit deflated in a suitcase-sized box and then fastened to a dead satellite. It’s then inflated to maximum size, and the huge bulk of the balloon massively increases the atmospheric drag that satellites experience up there in the void. This drag is due to the rare molecules of gas that hover around above the fringe of the atmosphere, and it’s the same drag that resulted in the premature deorbiting of the famous Skylab satellite in the 1970s, when the mechanics of orbital drag weren’t as well understood. The drag acts to slow a satellite in its orbital path, and then simple orbital mechanics means the satellite descends into the atmosphere where the denser air heats it to the point it burns up.

The World Gold Council has released a paper, Gold for Good: gold and nanotechnology in the age of innovation which highlights the many benefits of using gold nanoparticles in areas ranging from medicine to the environment. From the news item on Azonano,

The report, which was produced in conjunction with Cientifica Ltd, the world’s leading source of global business and investor intelligence about nanotechnologies, demonstrates how gold nanoparticles offer the potential to overcome many of the serious issues facing mankind over the coming decades.

Gold nanoparticles exhibit a variety of unique properties which, when harnessed and manipulated effectively, lead to materials whose uses are both far-ranging in their potential and cost effective. This report explores the many different applications that are being developed across the fields of health, environment and technology.

I found the report a useful (and rosy) overview of gold nanoparticles, their various benefits, and their potential for business investors as to be expected when one of the report’s authors is Tim Harper of the TNT Blog and principal of Cientifica. The report can be found here.

Michael Berger over at Nanowerk has written up a spotlight feature on a study about safety practices in nanotechnology laboratories that was published in Feb. 2010 in Nature Nanotechnology. From Nanowerk,

Published in the February issue of Nature Nanotechnology (“Reported nanosafety practices in research laboratories worldwide”), Jesus Santamaria, who heads the Nanostructured Films and Particles (NFP) Group at the University of Zaragoza, and his team have conducted an online survey to identify what safety practices researchers are following in their own labs.

“The results of our survey indicate that environmental health and safety practice in many research laboratories worldwide is lacking in several important aspects, and several reasons may contribute to this” Santamaria tells Nanowerk. “Toxicity of nanomaterials is a complex subject because it depends on multiple factors including size, surface area, chemical composition, shape, aggregation, surface coating and solubility. Furthermore, most published research emphasizes acute toxicity and mortality, rather than chronic exposure and morbidity.”

Meanwhile, Andrew Maynard at 2020 Science has written up a pointed critique. From Andrew,

Out of all those researchers surveyed who thought the materials they were using might become airborne at some stage, 21% didn’t use any form of “special protection” and 30% didn’t use respiratory protection. Yet there is no way of telling from the survey whether “special protection” (the authors’ terminology) was needed, or indeed whether any respiratory protection was needed. A researcher handling small amounts of fumed silica for example – used as a food additive amongst other places – might well handle it using established lab safety procedures that are entirely adequate and don’t include the use of a respirator – in this survey they would be classed in the category of “most researchers” not using “suitabe personal and laboratory protection.”

Unfortunately the Nature Nanotechnology article is behind a paywall but it is worth looking at Andrew’s critique both for the insight it gives you into laboratory practices and for a better understanding of the problems posed by the questions in the survey. Properly framing questions and the answers respondents get to choose from is one of the most difficult aspects of creating a questionnaire.

Andrew never mentions it and I can’t get past the paywall to find out but the questionnaire (or instrument as it’s often called) should have been tested before it was used. I suspect it was not. That said, testing won’t necessarily identify all the problems once you start dealing with a larger sample but it should help.

I have a couple of other comments. I didn’t see any mention of demographic information. For example, are they more careful in smaller labs or does lab size make any difference in safety processes? Does age or experience as a researcher have an impact? Are chemists more careful than physicists? Are men more careful than women or vice versa?

My second comment has to do with self-selected respondents. Why did these people respond to a survey? Generally, if you are surveying people about an issue, the most likely to respond are the ones who feel most strongly about the issue and this can give you a false picture of the general population. In other words, your sample is not generalizable. I don’t think that’s necessarily the situation here but it is a factor that needs to be taken into account. I would expect most social scientists (I gather the Spanish team is not composed of social scientists) to use a number of instruments and not just a self-reporting survey although that may be the first step as more work is undertaken.

I should mention the GoodNanoGuide as sharing handling and safety practices are the reasons this site was developed by the International Council on Nanotechnology (ICON). From their website,

The GoodNanoGuide is a collaboration platform designed to enhance the ability of experts to exchange ideas on how best to handle nanomaterials in an occupational setting.

Now for something completely different, Korean robot actresses. From the news item on physorg.com,

EveR-3 (Eve Robot 3) starred in various dramas last year including the government-funded “Dwarfs” which attracted a full house, said Lee Ho-Gil, of the state-run Korea Institute of Industrial Technology.

The lifelike EveR-3 is 157 centimetres (five feet, two inches) tall, can communicate in Korean and English, and can express a total of 16 facial expressions — without ever forgetting her lines. Lee acknowledged that robot actresses find it hard to express the full gamut of emotions and also tend to bump into props and fellow (human) actors. But he said a thespian android was useful in promoting the cutting-edge industry.

Here’s a shot of the robot actress as Snow White (from physorg.com where you can see a larger version if you wish),

Courtesy of the Korean Institute of Technology, Eve Robot 3 in costume for Robot Princess and 7 Dwarfs